*               },
   *               executor)
   *           .closing(executor);
   * }</pre>
   */
  // TODO(cpovirk): Use simple name instead of fully qualified after we stop building with JDK 8.
  @com.google.errorprone.annotations.DoNotMock(
      "Use ClosingFuture.whenAllSucceed() or .whenAllComplete() instead.")
  public static class Combiner {